Molecular Imaging Sees Red Blood Cells Move

Harvard University investigators announce the development of a non-invasive imaging technique that can be used to capture images of living tissues at the molecular level. The group reports that it was able to observe the passing of red blood cells through the capillaries of the vascular system.

The researchers made the observations on the living bodies of unsuspecting mice, raising hopes tha the same technique could soon be applied to humans as well. One of the most amazing thing about the new method is that it's noninvasive, the team says.

The way the technique woks is by using two interfering lasers – which operate at different frequencies – to excite different types of molecules inside the skin. A special detector picks up the molecular response to the laser interplay, and converts it into an image.

“To identify a solid tumor, tumor margins, and metastasis requires cutting and slicing tissue, staining it with dye, and looking at it under a microscope in a pathology lab next door – a process that could take 15 to 20 minutes,” explains Sunney Xie.

“Here, we don't need a biopsy; we can obtain almost identical images without cutting the tissue,” explains the expert, who is a Harvard professor of chemistry and chemical biology.

At this point, technologies such as magnetic resonance imaging (MRI) and positron emission tomography (PET) are the most commonly used methods of peering inside patients without using scalpels.

But each of them has its drawbacks. Patients that need MRI need to inject contrast agents, whereas those who have to get a PET scan need to subject themselves to low doses of radioactive materials.

But labels, as these materials are called, can also trigger alterations in the normal processes of cells. The new method is however label-free, non-invasive and based on a technique called Raman spectroscopy.

“If you have lots of pendulums, each one oscillates at the same frequency, but they are randomly distributed in their phase,” Xie explains of the method.

“That's what happens in conventional Raman spectroscopy. But here, we forced all the pendulums to go left and right at the same time, so in the end we have a much stronger signal,” he adds, quoted by Technology Review.

“This work should open new opportunities in studying chemical composition changes and drug transport,” explains Emory University professor of biomedical engineering Shuming Nie.

“This technique is dramatically more sensitive and [has] better spatial resolution, but it is still limited by very small penetration depths,” he concludes.